I found this comment on our partner site, MCADCentral.com in regards to creating this helix:
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xyzgeneral
Posted: 08 April 2006 at 10:28am | IP Logged Quote xyzgeneral

Hi all,

Use following set of equations (or click the links at the botom of the post) to create the curve (the so called Toroidal Spiral)

t=0
a=25
b=50
c=30
xt=(a*sin(360*c*t)+b)*cos(360*t)
yt=(a*sin(360*c*t)+b)*sin(360*t)
zt=a*cos(360*c*t)

Follow these steps : (UG NX2)

1)Enter above expessions using Tools->Expessions , 'c' is number of turns.

2)Inset->Cuve->Law Curve...

Choose 'by equation' option for xt, yt and zt values

3)Now create a datum plane by using Point on Curve option, select the curve ceated.

4)Select this datum plane to create Sketcher

while u r in sketcher mode, choose Insert->Associative point...

click Intersection point icon on Point Constructor dialog box, and select datum plane and curve respectively. Create a circle (say 5 units) and constrain its center to the above created associative point.

5)Use 'sweep along guide' or 'swept' to create the model.

Thats all folks!!!

U can refer to these links to know more about such equations :

http://www.salsburg.com/downloads/downloads.html
www.cs.csustan.edu/~rsc/SDSU/Math.projects.pdf
http://spirals.eternite.com/
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